Thanks for the tip, John - that sounds like a good one.

Do you know if it takes care of the common border problem? That is, if you
have a shapefile for, say, the 48 contiguous states, does it make sure that
common borders follow the same path for each polygon? A while back I tried a
standalone D-P algorithm written in Python, but it simplified each polygon
independently from the rest, so common borders ended up with all sorts of
gaps and overlaps. Not good at all.

Here's a program that does claim to handle this correctly and also uses
PostGIS. I haven't tried it out, though - no idea how it compares with the
built-in D-P code that you mentioned:

http://www.cartoweb.org/downloads/vertexsimplification/documentation.html

Also, for the OP, www.mapshaper.org seems to be back up now. It's a nice way
to do this interactively in just a few minutes, and it does handle common
borders well.

-Mike

> From: maps.huge.info [Maps API Guru]
> 
> I would suggest loading Postgresql 8.3.5 and PostGIS 1.3.3 on 
> your system, load in the shapefile and use the built in D-P 
> functions to do the task. There's a new function just added 
> to 1.3.3 called "ST_SimplifyPreserveTopology" that prevents 
> splinters and invalid polygons being formed by the D-P 
> process. Very cool! It's free to use and runs under virtually 
> any OS. To import a shapefile, use the shp2pgsql function and 
> to create shapefile from the database use pgsql2shp.
> 
> -John Coryat
> 
> http://maps.huge.info
> 
> http://www.usnaviguide.com


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